Quarterly Results Of Operations (Details) - USD ($)	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Quarterly Results Of Operations [Abstract]
Operating revenues	$ 57,741,954	$ 45,132,973	$ 44,622,517	$ 50,250,135	$ 50,640,703	$ 43,109,512	$ 47,697,820	$ 74,973,117	$ 197,747,579	$ 216,421,152	$ 281,318,513
Operating expenses	47,000,307	40,308,301	41,472,710	42,359,071	42,182,178	39,667,546	43,490,558	63,451,276	171,140,389	188,791,558	252,972,879
Net interest	5,341,242	5,427,440	5,247,404	5,385,211	5,415,131	5,428,774	5,381,167	5,589,373	21,401,297	21,814,445	22,800,706
Net operating margins	5,400,405	(602,768)	(2,097,597)	2,505,853	3,043,394	(1,986,808)	(1,173,905)	5,932,468	5,205,893	5,815,149	5,544,928
Nonoperating margins	231,683	125,332	127,871	123,077	368,403	79,028	126,010	114,262	607,963	687,703	970,617
Assignable margins	$ 5,632,088	$ (477,436)	$ (1,969,726)	$ 2,628,930	$ 3,411,797	$ (1,907,780)	$ (1,047,895)	$ 6,046,730	$ 5,813,856	$ 6,502,852	$ 6,515,545